1. Field of the Invention
The present invention relates to a liquid crystal display device. Further, the present invention relates to a technology to increase quality of a liquid crystal display device.
2. Description of the Related Art
In recent years, demand for a liquid crystal display device as a flat panel display has grown since the liquid crystal display device has advantages of thinness, lightweight and being capable of low-power-consumption driving. The liquid crystal display has various modes, and a liquid crystal display using a nematic liquid crystal includes a twisted nematic (TN) mode, a vertical alignment (VA) mode, an in plane switching (IPS) mode, an optically compensated bend (OCB) mode and the like. Further, a ferroelectric liquid crystal mode and an antiferroelectric liquid crystal mode in which a response speed is faster than in a nematic liquid crystal, are also proposed. In addition, polymer dispersed liquid crystal (PDLC) mode in which a liquid crystal is dispersed in a polymer molecule is also proposed.
Many other modes are proposed. However, a phenomenon that a liquid crystal transmits and does not transmit light in a liquid crystal display is basically performed by controlling birefringence, optical rotation, or scattering of the liquid crystal by applying voltage to the liquid crystal.
As a driving method for a liquid crystal display device, two kinds which are a passive driving method and an active matrix driving method are given. When a liquid crystal mode such as the TN mode, the VA mode or the OCB mode which is driven by applying voltage between upper and lower substrates, is operated in active matrix driving, voltage is applied through a flexible print circuit (FPC) which is attached to an active matrix substrate; therefore, in order to generate potential difference between the upper and lower substrates, a conductive portion (common contact portion) which makes a counter electrode of a counter substrate conductive to a connection wiring of the active matrix substrate, is required.
Generally, a method for forming the conductive portion is as follows: A sealant in which a conductor is mixed is applied to the conductive portion of either the upper substrate or the lower substrate, the upper and lower substrates are attached to each other, and the conductor which is formed at the conductive portion is in contact with the upper and lower substrates; therefore conductivity can be obtained.
However, in a case where the conductive portion is close to an insulating sealant for sealing the liquid crystal, in other words, in a case of a narrow frame, the conductive portion is covered by the sealant when the upper and lower substrates are attached to each other, and a conductive material cannot be in contact with both the upper and lower substrates or one side of the substrate; therefore a defect that conductivity cannot be obtained is occurred.
For this, a groove is formed at one of a pair of the substrates so that the above-described sealant which can cover the conductive portion goes into the groove (for example, refer to Patent Document 1)
However, in a case of using the above method, it is necessary to form a groove at one of the substrates by using laser and the like in advance, and the method has a problem that new steps are added, and the like.